Thrombin generation and inflammatory cytokines in canine immune-mediated Hemolytic Anemia

Abstract

Canine primary immune mediated hemolytic anemia (IMHA) is the most common immune mediated disorder of dogs. It causes acute and severe disease with a high mortality rate. Thromboembolism is a common and often fatal consequence of canine IMHA, and most deaths can be attributed to thromboembolic complications in these dogs. Recent research has tried to identify mechanisms causing thromboembolism in dogs with IMHA. Studies using viscoelastic testing have shown that dogs with IMHA are hypercoagulable. However, these tests are influenced by anemia, which is a feature of IMHA at diagnosis. Thrombin generation measurement using the calibrated automated thrombogram (CAT) is a promising method as it is a plasma-based assay and permits evaluation of the whole enzymatic potential of thrombin, and therefore could be correlated to the degree of inflammation in dogs with IMHA as well. In the present study, we showed that sample collection technique is a significant source of preanalytical variability and direct venipuncture is the recommended sampling technique. CAT appears to be a suitable test for canine thrombin generation. Clinically, dogs with IMHA displayed hypercoagulable features on CAT compared to healthy dogs with a significant elevation in peak thrombin generation. Non-survivors had a hypocoagulable CAT on presentation compared to healthy dogs and also compared to survivors. CAT was not better than previous coagulation parameter at predicting outcomes in IMHA. While newer immunosuppressant agents and better intensive care are available in veterinary medicine, the reported mortality rates for dogs with IMHA have remained relatively unchanged. Presently available immunosuppressive therapy broadly inhibits the immune system. Alteration of the IL-17 pathway may be central to the autoimmune and inflammatory response in IMHA. Serum IL-17 concentration remains significantly higher in IMHA non-survivors while it significantly decreases throughout hospitalization in survivors, making serum IL-17 a potential biomarker for severity and response to therapy in IMHA. Canine IMHA is a common and complex condition that results from multifactorial activation of the immune and hemostatic systems. This work opens new avenues for further investigation of IMHA and will hopefully lead to a better understanding and more targeted treatment of canine IMHA in the future.